I knocked up a batch of this, recipe #97 in the booklet, on 29th March. The recipe calls for Pale, Brown, Black malts and Fuggles or Goldings, so I reckon you've done a bit more tweaking than just the hops. I see I misguided enough to ferment it with S-04, probably didn't have anything else at the time. Anyway the blurb says ferment for 4-5 months and that time has expired so I'm going to try one this evening. I got an FG of 1012, by the way. Which isn't surprising with S-04.About three weeks ago now I did a second Durden Park malt recipe, sort of, which was bottled and thus tasted yesterday. This was the Whitbread London Porter from 1850, the recipe for which is posted up, along with the Simonds Bitter recipe on the Durden Park Website.
The Brown Malt for the recipe was also done from Pale malt in the oven, following the method outlined in the Appendix to the DP pamphlet.
You mention another Durden Park recipe, which calls for Pale Amber. Which one? I did a Simonds 1880 Bitter using Simpson's Imperial malt instead of making my own Pale Amber, and fermenting it with Opshaug. FG was 1010 and it was more light and fresh than the batch I made earlier fermented with West Yorkshire. Not sure which one I like the most, they're noticeably different. (Identical recipes only the yeasts changed).